1. Field of the Invention
The present invention relates to a lens barrel and more particularly, although not exclusively a lens barrel used in an imaging apparatus.
2. Description of the Related Art
Film cameras using silver-halide film and digital cameras capable of photographing with an image sensor have been conventionally well-known and widely used. In recent years, for the purpose of improving portability of a camera, the technical development of an internal mechanism of the camera has been performed in order to miniaturize the camera and to increase a rate of change of a focal length (zoom magnification), and, thus, various techniques have been proposed.
Conventional cameras include a zoom camera capable of changing the focal length of a photographic lens, and a monofocal camera having a fixed focal length lens. In these cameras, a lens barrel is generally provided which can extend and retract a photographic lens for the purpose of miniaturizing the camera at the non-photographing time (when the power source of the camera is turned off) or changing the focal length of the camera at the photographing time (when the power source of the camera is turned on).
In recent years, various mechanisms concentrating on slimming a camera have been proposed for realizing the simple portability of the camera. For slimming a camera, it is important to slim not only a battery or a liquid crystal display but also a lens barrel. For slimming a lens barrel, it is important to slim not only a photographic lens but also an internal mechanism of the camera, such as a shutter mechanism, a diaphragm mechanism, a focus adjusting mechanism, which are provided inside the lens barrel.
For example, a technique for sliming a lens barrel is discussed in Japanese Patent Application Laid-Open No. 2004-145029, in which a constituent member of the lens barrel is caused to recede from an optical axis to thereby reduce the depth of the lens barrel when the power source of the camera is turned off (when the lens barrel is in a retracted state)
Further, a similar construction as in the above technique is discussed in Japanese Patent Application Laid-Open No. 2003-315861, in which a photographic lens is caused to recede from an optical axis to thereby reduce the depth of the lens barrel when the lens barrel is in a retracted state.
Furthermore, a technique for miniaturizing a photographic lens is discussed in Japanese Patent Application Laid-Open No. 2004-053633, in which the positions of a diaphragm mechanism and a shutter mechanism are changed from a conventional arrangement to thereby reduce the depth of a lens barrel when the lens barrel is in a retracted state.
However, the techniques discussed in Japanese Patent Applications Laid-Open No. 2004-145029 and 2003-315861 may result in a cost increase, because an additional mechanism is needed to cause a member provided at the photographic lens to recede from the optical axis. Such a member is an infrared cut filter in Japanese Patent Application Laid-Open No. 2004-145029 or a photographic lens in Japanese Patent Application Laid-Open No. 2003-315861. Further, in the technique discussed in Japanese Patent Application Laid-Open No. 2003-315861, the photographic lens recedes from the optical axis to thereby reduce the depth of the lens barrel when the lens barrel is in a retracted state. However, a space for storing the receding photographic lens is needed, thus resulting in an increase in the diameter of the lens barrel. As the lens barrel is increased in size, the entire camera becomes large.
Further, in the technique discussed in Japanese Patent Application Laid-Open No. 2004-053633, the positions of the diaphragm mechanism and the shutter mechanism are changed from a conventional arrangement to thereby reduce the depth of the lens barrel when the lens barrel is in a retracted state. In this technique, the construction of an optical photographic lens is discussed, and the positions of the diaphragm mechanism and the shutter mechanism are also discussed. However, the construction of the photographic lens and the positions of the diaphragm mechanism and the shutter mechanism does not address completely the reduction of the depth of the lens barrel when the lens barrel is in a retracted state.